Production of TPO Roofing Membrane via Counter-Rotating Extrusion

ABSTRACT

The present disclosure is directed to a process for producing thermoplastic polyolefin roofing membrane. The process includes directly adding components of a high-load flame retardant TPO formulation to a counter-rotating twin screw extruder. The process includes extruding the formulation with counter-rotation of the twin screws and forming a TPO roofing membrane having a tensile strength of greater than 10 MPa and a flame retardance of rating of classification D as measured in accordance with EN ISO 1 1925-2, surface exposure test.

FIELD

The present disclosure is directed to a process for producing athermoplastic polyolefin roofing membrane.

BACKGROUND

Thermoplastic polyolefin (TPO) roofing membranes may be a single layeror may be composed of multiple layers and may contain a reinforcingfabric or scrim reinforcement material in the center between two layersof TPO membrane. A single layer of the TPO roofing membrane must exhibitweatherability (durability), flexibility, longevity, flame retardance,UV resistance, and chemical resistance. In addition, TPO roofingmembrane must be capable of forming hot-air welded seams. TPO roofingmembrane typically has a thickness from 35-90 mils, with the thicknessesof 45 mil, 60, mil, and 80 mil common industry standards.

Conventional TPO roofing membranes are typically produced in a directextrusion process on co-rotating twin screw extrusion lines. In directextrusion, the starting materials are directly fed into an extruder, sothat the melting, mixing and extrusion occur simultaneously. Co-rotatingtwin screw extrusion lines provide high throughput combined with mixingthat is capable of mixing high loads of granular flame retardant.

Despite the growing attraction for TPO roofing membranes, polyvinylchloride (PVC) roofing membranes still occupy a significant portion ofthe roofing market. In contrast to TPO membrane production, PVC roofingmembrane is typically produced on counter-rotating twin screw extrusionequipment which is suitable for the processing of polymers characterizedby low thermal stability (i.e., PVC).

Counter-rotating twin screw extrusion has its shortcomings when ahigh-load of filler is involved. Counter-rotating twin screw extrusiondoes not allow for even dispersion of high-load flame retardant inconventional TPO polymer systems. Pre-compounded starting material forTPO roofing membrane may be run on conventional PVC extrusion lines.However, the additional process step of compounding increases productionand labor expenditures making counter-rotation twin screw extrusion adisadvantaged option compared to co-rotating twin screw extrusion.Consequently, manufacturers of PVC roofing membrane are unable toproduce TPO roofing membrane on incumbent counter-rotating twin screwextrusion lines.

The art recognizes the need for a process capable of producing TPOroofing membrane on conventional counter-rotating twin screw extrusionplatforms. A need further exists for a process to produce TPO roofingmembrane without a compounding step and on a counter-rotating twin screwextruder system.

SUMMARY

The present disclosure is directed to a process for producing a TPOroofing membrane.

In an embodiment, the process includes directly adding components of ahigh-load flame retardant thermoplastic polyolefin (TPO) formulation toa counter-rotating twin screw extruder. The high-load flame retardantTPO formulation includes (i) an olefin block copolymer (ii) a polyolefinand (iii) greater than 30 wt % of a granular flame retardant. Theprocess further includes extruding, with counter-rotation of the twinscrews, the components of the high-load flame retardant TPO formulation.The process includes forming a TPO roofing membrane having a tensilestrength (CD) greater than 10 MPa and a flame retardance rating ofclassification D as measured in accordance with EN ISO 11925-2, surfaceexposure test.

In an embodiment, the process includes directly adding a high-load flameretardant TPO formulation to a counter-rotating twin screw extruder. Thehigh-load flame retardant includes (i) a propylene-based elastomer, (ii)a polyolefin, and (iii) greater than 30 wt % of a granular flameretardant. The process further includes extruding, with counter-rotationof the twin screws, the components of the high-load flame retardantformulation. The process includes forming a TPO roofing membrane havinga tensile strength (CD) greater than 10 MPa and a flame retardancerating of classification D as measured in accordance with EN ISO11925-2, surface exposure test.

An advantage of the present process is that the process enablesmanufacturers of PVC roofing membrane to produce TPO roofing membrane onconventional counter-rotating twin screw extrusion lines. PVC roofingmembrane manufacturers can offer TPO roofing membranes in their productportfolio without the need to invest in new equipment.

An advantage of the present disclosure is the ability to produceconventional PVC membrane and TPO roofing membrane on the same extrusionequipment.

DETAILED DESCRIPTION

A TPO roofing membrane must meet at least the following mechanicalproperties:

-   -   1. a tensile strength (CD and MD) greater than 10 MPa;    -   2. elongation at break (CD and MD) greater than 500%;    -   3. E-modulus (CD and MD) less than 100 MPa; and    -   4. a flame retardance rating of classification D as measured in        accordance with EN ISO 11925-2, surface exposure test.

The present disclosure provides a process for producing TPO roofingmembrane. In an embodiment, the process includes directly addingcomponents of a high-load flame retardant thermoplastic polyolefin (TPO)formulation to a counter-rotating twin screw (CRTS) extruder. Thehigh-load flame retardant TPO formulation includes at least threecomponents (i) an olefin block copolymer, (ii) a polyolefin, and (iii)greater than 30 wt % of a granular flame retardant. The process includesextruding, with counter-rotation of the twin screws, the components ofthe high-load flame retardant TPO formulation and forming a TPO roofingmembrane having a tensile strength (CD) greater than 10 MPa and a flameretardance a flame retardance rating of classification D as measured inaccordance with EN ISO 11925-2, surface exposure test.

Extrusion is a process by which a polymer is propelled continuouslyalong one or more screws through regions of high temperature andpressure where it is melted and compacted and finally forced through adie. The present process utilizes a counter-rotating twin screwextruder. A “counter-rotating twin screw extruder” (or “CRTS extruder”),as used herein, is an extruder with two parallel (or substantiallyparallel) intermeshing screws, the screws turning or rotating inopposing directions—one screw rotating in a clockwise direction and theother screw rotating in a counterclockwise direction.

The process includes directly adding components of a high-load flameretardant TPO formulation to a counter-rotating twin screw (CRTS)extruder. The term “directly adding,” or “direct addition,” or “directextrusion,” and like terms is the introduction of starting materialsinto the CRTS extruder with no prior compounding step.

Known are compounding procedures that entail physical blending devicesand that provide dispersive mixing, distributive mixing, or acombination thereof. Such compounding procedures are typically used toprepare homogeneous blends of starting materials prior to introductioninto the extruder. Nonlimiting examples of such compounding devicesinclude Brabender mixing devices and Banbury mixing devices.

The present process advantageously avoids the need for a compoundingprocedure prior to extrusion. In this way, the term “directly adding”excludes the compounding, mixing, or blending of the starting materialsprior to CRTS extrusion.

Components of the high-load flame retardant TPO formulation are directlyadded to the CRTS extruder. The components constitute the startingmaterials for the extrusion process. The term “high-load flame retardantTPO formulation” is a composition that includes at least onethermoplastic polyolefin, the composition also containing greater than30 wt % granular flame retardant. In an embodiment, the term “high-loadflame retardant TPO formulation” is a composition that includes at leastone thermoplastic polyolefin, the composition also containing from 35 wt% or 40 wt %, or 45 wt %, or 50 wt % to 60 wt %, or 65 wt %, or 70 wt %,or 75 wt % granular flame retardant. Weight percent is based on totalweight of the high-load flame retardant TPO formulation.

The formulation components may be added simultaneously or sequentiallyto the CRTS extruder. The formulation components may be addedcontinuously or intermittently to the CRTS extruder. In an embodiment,the formulation is prepared prior to introduction into the CRTSextruder. The formulation components are gathered in the desiredproportions. The formulation components are added directly to the CRTSextruder. However, no compounding of the formulation components occursprior to the addition to the CRTS extruder.

In an embodiment, the addition of the formulation components into theextruder occurs substantially simultaneously (all formulation componentsadded within 0-10 minutes or 0-5 minutes of each other), orsimultaneously. The flame retardant is fed into the CRTS extruderthrough a first port and the polymeric materials are added to the CRTSextruder through a second port. The melting, mixing is performed in asingle step. No compounding occurs prior to addition to the CRTSextruder.

1. Olefin Block Copolymer

The present high-load flame retardant TPO formulation includes at leastone thermoplastic polyolefin that is an olefin block copolymer. The term“olefin block copolymer” or “OBC” means an ethylene/α-olefin multi-blockcopolymer and includes ethylene and one or more copolymerizable α-olefincomonomer in polymerized form, characterized by multiple blocks orsegments of two or more polymerized monomer units differing in chemicalor physical properties. The terms “interpolymer” and “copolymer” areused interchangeably herein. When referring to amounts of “ethylene” or“comonomer” in the copolymer, it is understood that this meanspolymerized units thereof. In some embodiments, the multi-blockcopolymer can be represented by the following formula:

(AB)_(n)

Where n is at least 1, preferably an integer greater than 1, such as 2,3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or higher, “A”represents a hard block or segment and “B” represents a soft block orsegment. Preferably, As and Bs are linked in a substantially linearfashion, as opposed to a substantially branched or substantiallystar-shaped fashion. In other embodiments, A blocks and B blocks arerandomly distributed along the polymer chain. In other words, the blockcopolymers usually do not have a structure as follows:

AAA-AA-BBB-BB

In still other embodiments, the block copolymers do not usually have athird type of block, which comprises different comonomer(s). In yetother embodiments, each of block A and block B has monomers orcomonomers substantially randomly distributed within the block. In otherwords, neither block A nor block B comprises two or more sub-segments(or sub-blocks) of distinct composition, such as a tip segment, whichhas a substantially different composition than the rest of the block.

Preferably, ethylene comprises the majority mole fraction of the wholeblock copolymer, i.e., ethylene comprises at least 50 mole percent ofthe whole polymer. More preferably ethylene comprises at least 60 molepercent, at least 70 mole percent, or at least 80 mole percent, with thesubstantial remainder of the whole polymer comprising at least one othercomonomer that is preferably an α-olefin having 3 or more carbon atoms.In some embodiments, the olefin block copolymer may comprise 50 mol % to90 mol % ethylene, preferably 60 mol % to 85 mol %, more preferably 65mol % to 80 mol %. For many ethylene/octene block copolymers, thepreferred composition comprises an ethylene content greater than 80 molepercent of the whole polymer and an octene content of from 10 to 15,preferably from 15 to 20 mole percent of the whole polymer.

The olefin block copolymer includes various amounts of “hard” and “soft”segments. “Hard” segments are blocks of polymerized units in whichethylene is present in an amount greater than 95 weight percent, orgreater than 98 weight percent based on the weight of the polymer, up to100 weight percent. In other words, the comonomer content (content ofmonomers other than ethylene) in the hard segments is less than 5 weightpercent, or less than 2 weight percent based on the weight of thepolymer, and can be as low as zero. In some embodiments, the hardsegments include all, or substantially all, units derived from ethylene.“Soft” segments are blocks of polymerized units in which the comonomercontent (content of monomers other than ethylene) is greater than 5weight percent, or greater than 8 weight percent, greater than 10 weightpercent, or greater than 15 weight percent based on the weight of thepolymer. In some embodiments, the comonomer content in the soft segmentscan be greater than 20 weight percent, greater than 25 weight percent,greater than 30 weight percent, greater than 35 weight percent, greaterthan 40 weight percent, greater than 45 weight percent, greater than 50weight percent, or greater than 60 weight percent and can be up to 100weight percent.

The soft segments can be present in an OBC from 1 weight percent to 99weight percent of the total weight of the OBC, or from 5 weight percentto 95 weight percent, from 10 weight percent to 90 weight percent, from15 weight percent to 85 weight percent, from 20 weight percent to 80weight percent, from 25 weight percent to 75 weight percent, from 30weight percent to 70 weight percent, from 35 weight percent to 65 weightpercent, from 40 weight percent to 60 weight percent, or from 45 weightpercent to 55 weight percent of the total weight of the OBC. Conversely,the hard segments can be present in similar ranges. The soft segmentweight percentage and the hard segment weight percentage can becalculated based on data obtained from DSC or NMR. Such methods andcalculations are disclosed in, for example, U.S. Pat. No. 7,608,668,entitled “Ethylene/α-Olefin Block Inter-polymers,” filed on Mar. 15,2006, in the name of Colin L. P. Shan, Lonnie Hazlitt, et. al. andassigned to Dow Global Technologies Inc., the disclosure of which isincorporated by reference herein in its entirety. In particular, hardand soft segment weight percentages and comonomer content may bedetermined as described in Column 57 to Column 63 of U.S. Pat. No.7,608,668.

The olefin block copolymer is a polymer comprising two or morechemically distinct regions or segments (referred to as “blocks”)preferably joined in a linear manner, that is, a polymer comprisingchemically differentiated units which are joined end-to-end with respectto polymerized ethylenic functionality, rather than in pendent orgrafted fashion. In an embodiment, the blocks differ in the amount ortype of incorporated comonomer, density, amount of crystallinity,crystallite size attributable to a polymer of such composition, type ordegree of tacticity (isotactic or syndiotactic), regio-regularity orregio-irregularity, amount of branching (including long chain branchingor hyper-branching), homogeneity or any other chemical or physicalproperty. Compared to block interpolymers of the prior art, includinginterpolymers produced by sequential monomer addition, fluxionalcatalysts, or anionic polymerization techniques, the present OBC ischaracterized by unique distributions of both polymer polydispersity(PDI or Mw/Mn or MWD), block length distribution, and/or block numberdistribution, due, in an embodiment, to the effect of the shuttlingagent(s) in combination with multiple catalysts used in theirpreparation.

In an embodiment, the OBC is produced in a continuous process andpossesses a polydispersity index, PDI, from 1.7 to 3.5, or from 1.8 to3, or from 1.8 to 2.5, or from 1.8 to 2.2. When produced in a batch orsemi-batch process, the OBC possesses PDI from 1.0 to 3.5, or from 1.3to 3, or from 1.4 to 2.5, or from 1.4 to 2.

In addition, the olefin block copolymer possesses a PDI fitting aSchultz-Flory distribution rather than a Poisson distribution. Thepresent OBC has both a polydisperse block distribution as well as apolydisperse distribution of block sizes. This results in the formationof polymer products having improved and distinguishable physicalproperties. The theoretical benefits of a polydisperse blockdistribution have been previously modeled and discussed in Potemkin,Physical Review E (1998) 57 (6), pp. 6902-6912, and Dobrynin, J. Chem.Phys. (1997) 107 (21), pp 9234-9238.

In an embodiment, the present olefin block copolymer possesses a mostprobable distribution of block lengths. In an embodiment, the olefinblock copolymer is defined as having:

(A) Mw/Mn from 1.7 to 3.5, at least one melting point, Tm, in degreesCelsius, and a density, d, in grams/cubic centimeter, where in thenumerical values of Tm and d correspond to the relationship:

Tm>−2002.9+4538.5(d)−2422.2(d)²,

-   -   where d is from 0.850 g/cc, or 0.860, or 0.866 g/cc, or 0.87        g/cc, or 0.880 g/cc to 0.89 g/cc, or 0.91 g/cc, or 0.925 g/cc,        and    -   Tm is from 113° C., or 115° C., or 117° C., or 118° C. to 120°        C., or 121° C., or 125° C.; and/or

(B) Mw/Mn from 1.7 to 3.5, and is characterized by a heat of fusion, ΔHin J/g, and a delta quantity, ΔT, in degrees Celsius defined as thetemperature difference between the tallest DSC peak and the tallestCrystallization Analysis Fractionation (“CRYSTAF”) peak, wherein thenumerical values of ΔT and ΔH have the following relationships:

ΔT>−0.1299ΔH+62.81 for ΔH greater than zero and up to 130 J/g

ΔT>48° C. for ΔH greater than 130 J/g

wherein the CRYSTAF peak is determined using at least 5 percent of thecumulative polymer, and if less than 5 percent of the polymer has anidentifiable CRYSTAF peak, then the CRYSTAF temperature is 30° C.;and/or

(C) elastic recovery, Re, in percent at 300 percent strain and 1 cyclemeasured with a compression-molded film of the ethylene/α-olefininterpolymer, and has a density, d, in grams/cubic centimeter, whereinthe numerical values of Re and d satisfy the following relationship whenethylene/α-olefin interpolymer is substantially free of crosslinkedphase:

Re>1481−1629(d); and/or

(D) has a molecular fraction which elutes between 40° C. and 130° C.when fractionated using TREF, characterized in that the fraction has amolar comonomer content greater than, or equal to, the quantity(−0.2013)T+20.07, more preferably greater than or equal to the quantity(−0.2013)T+21.07, where T is the numerical value of the peak elutiontemperature of the TREF fraction, measured in ° C.; and/or,

(E) has a storage modulus at 25° C., G′(25° C.), and a storage modulusat 100° C., G′(100° C.), wherein the ratio of G′(25° C.) to G′(100° C.)is in the range of 1:1 to 9:1.

The olefin block copolymer may also have:

(F) a molecular fraction which elutes between 40° C. and 130° C. whenfractionated using TREF, characterized in that the fraction has a blockindex of at least 0.5 and up to 1 and a molecular weight distribution,Mw/Mn, greater than 1.3; and/or

(G) average block index greater than zero and up to 1.0 and a molecularweight distribution, Mw/Mn greater than 1.3. It is understood that theolefin block copolymer may have one, some, all, or any combination ofproperties (A)-(G). Block Index can be determined as described in detailin U.S. Pat. No. 7,608,668 herein incorporated by reference for thatpurpose. Analytical methods for determining properties (A) through (G)are disclosed in, for example, U.S. Pat. No. 7,608,668, Col. 31, line 26through Col. 35, line 44, which is herein incorporated by reference forthat purpose.

Suitable monomers for use in preparing the present OBC include ethyleneand one or more addition polymerizable monomers other than ethylene.Examples of suitable comonomers include straight-chain or branchedα-olefins of 3 to 30, preferably 3 to 20, carbon atoms, such aspropylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene,4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene; cyclo-olefinsof 3 to 30, preferably 3 to 20, carbon atoms, such as cyclopentene,cycloheptene, norbornene, 5-methyl-2-norbornene, tetracyclododecene, and2-methyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene; di-and polyolefins, such as butadiene, isoprene, 4-methyl-1,3-pentadiene,1,3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, 1,4-hexadiene,1,3-hexadiene, 1,3-octadiene, 1,4-octadiene, 1,5-octadiene,1,6-octadiene, 1,7-octadiene, ethylidenenorbornene, vinyl norbornene,dicyclopentadiene, 7-methyl-1,6-octadiene,4-ethylidene-8-methyl-1,7-nonadiene, and 5,9-dimethyl-1,4,8-decatriene;and 3-phenylpropene, 4-phenylpropene, 1,2-difluoroethylene,tetrafluoroethylene, and 3,3,3-trifluoro-1-propene.

The olefin block copolymer has a density of from 0.850 g/cc to 0.925g/cc, or from 0.860 g/cc to 0.88 g/cc or from 0.860 g/cc to 0.879 g/cc.The OBC has a Shore A value of 40 to 70, preferably from 45 to 65 andmore preferably from 50 to 65. In an embodiment, the olefin blockcopolymer has a melt index (MI) from 0.1 g/10 min to 30 g/10, or from0.1 g/10 min to 20 g/10 min, or from 0.1 g/10 min to 15 g/10 min, asmeasured by ASTM D 1238 (190° C./2.16 kg). The formulation may comprisemore than one olefin block copolymer.

The olefin block copolymers can be produced via a chain shuttlingprocess such as described in U.S. Pat. No. 7,858,706, which is hereinincorporated by reference. In particular, suitable chain shuttlingagents and related information are listed in Col. 16, line 39 throughCol. 19, line 44. Suitable catalysts are described in Col. 19, line 45through Col. 46, line 19 and suitable co-catalysts in Col. 46, line 20through Col. 51 line 28. The process is described throughout thedocument, but particularly in Col. Col 51, line 29 through Col. 54, line56. The process is also described, for example, in the following: U.S.Pat. No. 7,608,668; U.S. Pat. No. 7,893,166; and U.S. Pat. No.7,947,793.

In an embodiment, the olefin block copolymer is an ethylene/octenemulti-block copolymer with a density from 0.86 g/cc to 0.88 g/cc, a Tmfrom 118° C.-120° C., a melt index from 0.5 g/10 min to 5.0 g/10 min.,and a Mw/Mn from 1.7 to 3.5.

The olefin block copolymer may comprise two or more embodimentsdescribed herein.

2. Olefin-Based Polymer

The high-load flame retardant TPO formulation includes an olefin-basedpolymer. The olefin-based polymer is different than the olefin blockcopolymer. The term, “olefin-based polymer,” as used herein, refers to apolymer that comprises, in polymerized form, a majority amount of olefinmonomer, for example ethylene or propylene (based on the weight of thepolymer), and optionally may comprise one or more comonomers.

In an embodiment, the olefin-based polymer is an ethylene-based polymer.The term, “ethylene-based polymer,” as used herein, refers to a polymerthat comprises, in polymerized form, a majority amount of ethylenemonomer (based on the weight of the polymer), and optionally maycomprise one or more comonomers. The ethylene-based polymer may be (i) aZiegler-Natta catalyzed ethylene copolymer comprising repeating unitsderived from ethylene and one or more α-olefins having from 3 to 10carbon atoms; (ii) a metallocene-catalyzed ethylene copolymer comprisingrepeating units derived from ethylene and one or more α-olefins havingfrom 3 to 10 carbon atoms; (iii) a Ziegler-Natta-catalyzed ethylenehomopolymer; (iv) a metallocene-catalyzed ethylene homopolymer; andcombinations thereof.

A. Ethylene/α-Olefin Copolymer

In an embodiment, the ethylene-based polymer is an ethylene/α-olefincopolymer. The term “ethylene/α-olefin copolymer,” as used herein,refers to a copolymer that comprises, in polymerized form, a majorityamount of ethylene monomer (based on the weight of the copolymer), andan α-olefin, as the only two monomer types. The ethylene/α-olefincopolymer can include ethylene and one or more C₃-C₂₀ α-olefincomonomers. The comonomer(s) can be linear or branched. Nonlimitingexamples of suitable comonomers include propylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, and 1-octene. The ethylene/α-olefincopolymer can be prepared with either Ziegler-Natta, chromium-based,constrained geometry or metallocene catalysts in slurry reactors, gasphase reactors or solution reactors. The ethylene/α-olefin copolymer isa random copolymer and is distinct from the OBC which has a blockintra-molecular architecture.

In an embodiment, the ethylene/α-olefin copolymer has a density rangewith a lower limit from 0.90 g/cc, or 0.91 g/cc, or 0.920 g/cc or 0.93g/cc, to an upper limit of 0.94 g/cc, or 0.950 g/cc, or 0.96 g/cc. In anembodiment, the ethylene/α-olefin copolymer has a density from 0.90 g/ccto 0.910 g/cc. In an embodiment, the ethylene/α-olefin copolymer has amelt index from 0.5 g/10 min to 5 g/10 min.

In an embodiment, the ethylene/α-olefin copolymer has a density from0.90 g/cc to 0.91 g/cc and a melt index from 1.0 g/10 min to 5.0 g/10min.

In an embodiment, the ethylene/α-olefin copolymer has a density from0.93 g/cc to 0.95 g/cc and a melt index from 0.5 g/10 min to 1.0 g/10min.

Nonlimiting examples of suitable ethylene/α-olefin copolymer includepolyethylene sold under the trade names ATTANE, DOWLEX, or ELITEavailable from The Dow Chemical Company.

B. Propylene-Based Elastomer

In an embodiment, the olefin-based polymer is a propylene-basedelastomer. A “propylene-based elastomer” (or “PBE”) comprises at leastone copolymer with at least 50 weight percent of units derived frompropylene and at least about 5 weight percent of units derived from acomonomer other than propylene, such as ethylene for example.

The PBE is characterized as having substantially isotactic propylenesequences. “Substantially isotactic propylene sequences” means thesequences have an isotactic triad (mm) measured by ¹³C NMR of greaterthan 0.85, or greater than 0.90, or greater than 0.92, or greater than0.93. Isotactic triads are known in the art and described in, forexample, U.S. Pat. No. 5,504,172 and WO 2000/01745, which refer to theisotactic sequence in terms of a triad unit in the copolymer molecularchain determined by ¹³C NMR spectra.

The PBE has a melt flow rate (MFR) in the range of from 0.1 to 25 g/10minutes (min.), measured in accordance with ASTM D-1238 (at 230° C./2.16Kg). All individual values and subranges from 0.1 to 25 g/10 min. areincluded and disclosed herein; for example, the MFR can be from a lowerlimit of 0.1, 0.2, or 0.5, to an upper limit of 25, 15, 10, 8, or 5,g/10 min. For example, PBE that is propylene/ethylene copolymer may havea MFR in the range of 0.1 to 10, or in the alternative, 0.2 to 10, g/10min.

The PBE has a crystallinity in the range of from at least 1 to 30 wt %(a heat of fusion of at least 2 to less than 50 Joules/gram (J/g)), allindividual values and subranges thereof being included and disclosedherein. For example, the crystallinity can be from a lower limit of 1,2.5, or 3, wt % (respectively, at least 2, 4, or 5 J/g) to an upperlimit of 30, 24, 15 or 7, wt % (respectively, less than 50, 40, 24.8 or11 J/g). For example, PBE that is propylene/ethylene copolymer may havea crystallinity in the range from at least 1 to 24, 15, 7, or 5, wt %(respectively, at least 2 to less than 40, 24.8, 11, or 8.3 J/g).Crystallinity is measured via DSC method, as described below in the testmethods section. The propylene/ethylene copolymer comprises unitsderived from propylene and polymeric units derived from ethylenecomonomer and optional C₄-C₁₀ α-olefin. Exemplary comonomers are C₂, andC₄ to C₁₀ α-olefins; for example, C₂, C₄, C₆ and C₈ α-olefins.

In an embodiment, the PBE comprises from 1 wt % to 40 wt % ethylenecomonomer. All individual values and subranges from 1 wt % to 40 wt %are included and disclosed herein; for example, the comonomer contentcan be from a lower limit of 1, 3, 4, 5, 7 or 9, wt % to an upper limitof 40, 35, 30, 27, 20, 15, 12 or 9, wt %. For example, thepropylene/ethylene copolymer comprises from 1 to 35 wt %, or, inalternative, from 1 to 30, 3 to 27, 3 to 20, or from 3 to 15, wt %, ofethylene comonomer.

In an embodiment, the PBE has a density from 0.850 g/cc, or 0.860 g/cc,or 0.865 g/cc to 0.900 g/cc.

In an embodiment, the PBE has a molecular weight distribution (MWD),defined as weight average molecular weight divided by number averagemolecular weight (M_(w)/M_(n)) of 3.5 or less; in the alternative 3.0 orless; or in another alternative from 1.8 to 3.0.

Such PBE types of polymers are further described in U.S. Pat. Nos.6,960,635 and 6,525,157, incorporated herein by reference. Such PBE iscommercially available from The Dow Chemical Company, under the tradename VERSIFY, or from ExxonMobil Chemical Company, under the trade nameVISTAMAXX.

In an embodiment, the PBE is further characterized as comprising (A)between 60 and less than 100, between 80 and 99, or between 85 and 99,wt % units derived from propylene, and (B) between greater than zero and40, or between 1 and 20, 4 and 16, or between 4 and 15, wt % unitsderived from ethylene and optionally one or more C₄₋₁₀ α-olefin; andcontaining an average of at least 0.001, at least 0.005, or at least0.01, long chain branches/1000 total carbons, wherein the term longchain branch refers to a chain length of at least one (1) carbon morethan a short chain branch, and wherein short chain branch refers to achain length of two (2) carbons less than the number of carbons in thecomonomer. For example, a propylene/1-octene interpolymer has backboneswith long chain branches of at least seven (7) carbons in length, butthese backbones also have short chain branches of only six (6) carbonsin length. The maximum number of long chain branches in thepropylene/ethylene copolymer interpolymer does not exceed 3 long chainbranches/1000 total carbons.

In an embodiment, the PBE copolymer has a melt temperature (Tm) from 55°C. to 146° C.

A nonlimiting example of a suitable propylene/ethylene copolymer isVERSIFY 3300, available from The Dow Chemical Company.

C. Propylene-Based Polymer

In an embodiment, the olefin-based polymer is a propylene-based polymer.The term, “propylene-based polymer,” as used herein, refers to a polymerthat comprises, in polymerized form, a majority amount of propylenemonomer (based on the weight of the polymer), and optionally maycomprise one or more comonomers. The propylene-based polymer may be (i)a Ziegler-Natta catalyzed propylene copolymer comprising repeating unitsderived from propylene and one or more α-olefins having from 2 or 4 to10 carbon atoms (ethylene is considered an α-olefin for purposes of thepresent disclosure); (ii) a metallocene-catalyzed propylene/α-olefincopolymer comprising repeating units derived from propylene and one ormore α-olefins having from 2, or 4 to 10 carbon atoms; (iii) aZiegler-Natta-catalyzed propylene homopolymer; (iv) ametallocene-catalyzed propylene homopolymer; and combinations thereof.

In an embodiment, the propylene-based polymer is a propylene impactcopolymer. Propylene impact copolymer is a two-phase polymer wherein adiscontinuous phase of propylene/ethylene copolymer is dispersedthroughout a continuous phase of propylene homopolymer.

The olefin-based polymer may comprise two or more embodiments disclosedherein.

3. Flame Retardant

The high-load flame retardant thermoplastic polyolefin (TPO) formulationincludes greater than 30 wt % flame retardant. The flame retardant is asolid in granular form or in powder form. In an embodiment, thehigh-load flame retardant TPO formulation includes flame retardant at alower limit of 35 wt %, or 40 wt %, or 45 wt %, or 50 wt % to an upperlimit of 55 wt %, or 60 wt %, or 65 wt %, or 70 wt %, or 75 wt %. Weightpercent is based on the total weight of the high-load flame retardantTPO formulation.

In an embodiment, the high-load flame retardant TPO formulation includesfrom 40 wt %, or 45 wt %, or 55 wt %, to 55 wt %, or 60 wt %, or 65 wt %of flame retardant.

In an embodiment, the high-load flame retardant TPO formulation includesgreater than 50 wt % flame retardant, or from greater than 50 wt % to 75wt % flame retardant.

Nonlimiting examples of suitable flame retardant include aluminahydroxide (ATH), magnesium hydroxide (MDH), huntite/hydromagnesite, N-and P-based flame retardants (e.g., melamine-poly(aluminumphosphate) ormelamine-poly(zincphosphate)), calcium carbonate, zinc oxide, aluminumsilicate, calcium silicate, barium sulfate, titanium dioxide, antimonyoxide, titanates, borates, mica, talc, glass (such as glass fiber andglass microspheres), nano-clay, and combinations thereof.

In an embodiment, the flame retardant is halogen-free. A “halogen-freeflame retardant” is a flame retardant the is void of halogen atom (F,Cl, Br, I).

The flame retardant may comprise two or more embodiments describedherein.

4. Additives

The high-load flame retardant TPO may include one or more optionaladditives. Suitable additives include, but are not limited to,antioxidants, UV stabilizers, foaming agents, colorants or pigments, andcombinations thereof.

In an embodiment, the high-load flame retardant (TPO) formulationincludes from 1 wt % to 5 wt % of an additive package. The additivepackage includes a propylene-based elastomer carrier, a thermalstabilizer, a hindered amine light stabilizer (HALS), and titaniumdioxide. The additive package includes from 30 wt % to 40 wt % of thepropylene-based elastomer carrier, from 1 wt % to 5 wt % of the thermalstabilizer, from 5 wt % to 15 wt % of the HALS, and from 45 wt % to 55wt % of titanium dioxide.

The process includes extruding the components of the high-load flameretardant TPO formulation and forming a TPO roofing membrane with atensile strength greater than 10 MPa (CD), and a flame retardance ratingof classification D as measured in accordance with EN ISO 11925-2,surface exposure test. Extrusion occurs by way of counter-rotation ofthe twin screws at elevated temperature (greater than ambienttemperature). In an embodiment, the process includes extruding thehigh-load flame retardant TPO formulation at a temperature less than185° C. In a further embodiment, the process includes extruding thehigh-load flame retardant TPO formulation at a temperature range with alower limit of 120° C., or 130° C., or 140° C., or 150° C. to an upperlimit of 160° C., or 170° C., or 175° C., or 180° C. or less than 185°C.

In an embodiment, the process includes extruding the components of thehigh-load flame retardant TPO formulation and forming a TPO roofingmembrane with a flame retardance rating of classification D as measuredin accordance with EN ISO 11925-2 for both the surface exposure test andthe edge exposure test.

In an embodiment, the process includes counter-rotating the twin screwsat a rotation rate from 15 rotations per minute (rpm), or 20 rpm, or 25rpm to 30 rpm, or 35 rpm, or 40 rpm.

Applicant surprisingly discovered a formulation composed of solely solidcomponents that unexpectedly works synergistically upon direct addition(no compounding step) to the CRTS extruder to promote homogeneousdispersion of the high-load flame retardant throughout the polymericcomponents. The present high-load flame retardant TPO formulation andCRTS extruder work synergistically to produce TPO roofing membrane thatmeets, or exceeds, the mechanical and flame retardant properties of TPOroofing membrane made on co-rotating twin screw extruders.

In an embodiment, the process includes directly adding, to the CRTSextruder, a high-load TPO formulation composed of:

-   -   20 wt % to 50 wt % olefin block copolymer;    -   10 wt % to 30 wt % ethylene/α-olefin copolymer; and    -   35 wt % to 75 wt % of a flame retardant.

The process further includes forming a TPO roofing membrane having thefollowing properties:

-   -   a tensile strength greater than 10 MPa;    -   an elongation at break greater than 500%;    -   an E-modulus less than 100 MPa; and    -   a flame retardance rating of classification D as measured in        accordance with EN ISO 11925-2, for the surface exposure test        and the edge exposure test.

In a further embodiment, the TPO roofing membrane has a flame retardancerating of classification D as measured in accordance with EN ISO11925-2, for the surface exposure test and the edge exposure test.

In an embodiment, the process includes directly adding, to the CRTSextruder components of a high-load flame retardant TPO formulationcomposed of the following components:

-   -   20 wt % to 40 wt % olefin block copolymer;    -   15 wt % to 30 wt % ethylene/α-olefin copolymer having a density        from 0.90 g/cc to 0.91 g/cc;    -   35 wt % to 60 wt % of a flame retardant; and    -   1 wt % to 5 wt % additive.

The process further includes forming a TPO roofing membrane. The TPOroofing membrane has the following properties:

-   -   a tensile strength from greater than 10 MPa to 25 MPa;    -   an elongation at break from greater than 500% to 1100%;    -   an E-modulus less than 100 MPa; and    -   a flame retardance rating of classification D as measured in        accordance with EN ISO 11925-2, for the surface exposure test        alone, or in combination with the edge exposure test.

The process may comprise two or more embodiments disclosed herein.

5. Process-PBE

The present disclosure provides another process. In an embodiment theprocess comprises:

directly adding components of a high-load flame retardant thermoplasticpolyolefin (TPO) formulation to a counter-rotating twin screw extruder,the high-load flame retardant TPO formulation comprising

-   -   a propylene-based elastomer (PBE);    -   a polyolefin;    -   greater than 30 wt % of a granular flame retardant;

extruding, with counter-rotation of the twin screws, the components ofthe high-load flame retardant TPO formulation; and

forming a TPO roofing membrane having

-   -   a tensile strength (CD) greater than 10 MPa, and    -   a flame retardance rating of classification D as measured in        accordance with EN ISO 11925-2, surface exposure test. The        foregoing process is hereafter referred to as “Process-PBE.”        Process-PBE utilizes PBE, or a blend of PBE and OBC, rather than        OBC.

In an embodiment, Process-PBE comprises forming a TPO roofing membranehaving a flame retardance rating of classification D as measured inaccordance with EN ISO 11925-2, for the surface exposure test and theedge exposure test.

In an embodiment, Process-PBE comprises counter-rotating the twin screwsat a rotation rate from 15 rpm to 40 rpm.

In an embodiment, Process-PBE comprises performing the counter-rotatingextrusion at a temperature less than 185° C.

In an embodiment, Process-PBE comprises directly adding components of ahigh-load TPO formulation comprising

-   -   20 wt % to 50 wt % PBE;    -   10 wt % to 30 wt % propylene-based polymer;    -   35 wt % to 75 wt % of a flame retardant; and

forming a TPO roofing membrane having

-   -   a tensile strength (CD) greater than 10 MPa;    -   an elongation at break greater than 500%; and    -   an E-modulus less than 100 MPa. The TPO roofing membrane has a        flame retardance rating of classification D as measured in        accordance with EN ISO 11925-2 for the surface exposure test,        alone or in combination with the edge exposure test.

In an embodiment, Process-PBE comprises directly adding components of ahigh-load flame retardant TPO formulation comprising

-   -   40 wt % to 60 wt % PBE;    -   10 wt % to 15 wt % propylene-based polymer that is a propylene        impact copolymer;    -   30 wt % to 40 wt % of a flame retardant;    -   1 wt % to 5 wt % additive; and

forming a TPO roofing membrane having

-   -   a tensile strength from greater than 10 MPa to 25 MPa;    -   an elongation at break from greater than 500% to 1100%; and    -   an E-modulus less than 100 MPa. The TPO roofing membrane has a        flame retardance rating of classification D as measured in        accordance with EN ISO 11925-2 for the surface exposure test,        alone or in combination with the edge exposure test.

The Process-PBE may comprise two or more embodiments disclosed herein.

DEFINITIONS

Unless stated to the contrary, implicit from the context, or customaryin the art, all parts and percents are based on weight, and all testmethods are current as of the filing date of this disclosure.

The term “composition,” as used herein, refers to a mixture of materialswhich comprise the composition, as well as reaction products anddecomposition products formed from the materials of the composition.

The terms “comprising,” “including,” “having,” and their derivatives,are not intended to exclude the presence of any additional component,step or procedure, whether or not the same is specifically disclosed. Inorder to avoid any doubt, all compositions claimed through use of theterm “comprising” may include any additional additive, adjuvant, orcompound, whether polymeric or otherwise, unless stated to the contrary.In contrast, the term, “consisting essentially of” excludes from thescope of any succeeding recitation any other component, step orprocedure, excepting those that are not essential to operability. Theterm “consisting of” excludes any component, step or procedure notspecifically delineated or listed.

The term “polymer,” as used herein, refers to a polymeric compoundprepared by polymerizing monomers, whether of the same or a differenttype. The generic term polymer thus embraces the term homopolymer(employed to refer to polymers prepared from only one type of monomer,with the understanding that trace amounts of impurities can beincorporated into the polymer structure), and the term interpolymer asdefined hereinafter.

The term “interpolymer,” as used herein, refers to polymers prepared bythe polymerization of at least two different types of monomers. Thegeneric term interpolymer thus includes copolymers (employed to refer topolymers prepared from two different types of monomers), and polymersprepared from more than two different types of monomers.

Test Methods Melt Index

Melt index (I2) is measured in accordance with ASTM D-1238 (190° C.;2.16 kg). The result is reported in grams/10 minutes. Melt flow rate(MFR) is measured in accordance with ASTM D-1238 (230° C.; 2.16 kg). Theresult is reported in grams/10 minutes.

Density

Density is measured in accordance with ASTM D-792.

Flame Retardance

Flame retardance is measured in accordance with EN ISO 11925-2. In theignitability test EN ISO 11925-2, a specimen is subjected to directimpingement of a small flame. The test specimen of size 250 mm×90 mm isattached vertically on a U-shaped specimen holder. A propane gas flamewith a height of 20 mm is brought into contact with the specimen at anangle of 45°. The application point is either 40 mm above the bottomedge of the surface center-line (surface exposure test) or at the centerof the width of the bottom edge (edge exposure test). Filter paper isplaced beneath the specimen holder to monitor the falling of flamingdebris.

Two different flame application times and test durations are useddepending on the class of the product. For class E, the flameapplication time is 15 seconds, and the test is terminated 35 secondsafter the removal of the flame. With a flame application time of 30seconds for classes B, C and D, the maximum duration of the test is 60seconds after the removal of the flame. The test is terminated earlierif no ignition is observed after the removal of the flame source, or thespecimen ceases to burn (or glow), or the flame tip reaches the upperedge of the specimen.

The classification criteria are based on observations whether the flamespread (Fs) reaches 150 mm within a given time and whether the filterpaper below the specimen ignites due to flaming debris. In addition, theoccurrence and duration of flaming and glowing are observed.

-   -   EN ISO 11925-2

B class ignition time = 30 sec, 60 sec Fs ≦ 150 mm C class ignition time= 30 sec, 60 sec Fs ≦ 150 mm D class ignition time = 30 sec, 60 sec Fs ≦150 mm E class ignition time = 15 sec, 35 sec Fs ≦ 150 mm

A specimen meets classification D if the following two conditions aremet:

-   -   (1) Fs≦150 mm for 60 second test time    -   (2) No burning droplets

Gel Permeation Chromatography (GPC)

Conventional GPC measurements are used to determine the weight-average(Mw) and number-average (Mn) molecular weight of the polymer, and todetermine the MWD (=Mw/Mn). “Samples are analyzed with ahigh-temperature GPC instrument (Polymer Laboratories, Inc. modelPL220).

The method employs the well-known universal calibration method, based onthe concept of hydrodynamic volume, and the calibration is performedusing narrow polystyrene (PS) standards, along with four Mixed A 20 μmcolumns (PLgel Mixed A from Agilent (formerly Polymer Laboratory Inc.))operating at a system temperature of 140° C. Samples are prepared at a“2 mg/mL” concentration in 1,2,4-trichlorobenzene solvent. The flow rateis 1.0 mL/min, and the injection size is 100 microliters.

As discussed, the molecular weight determination is deduced by usingnarrow molecular weight distribution polystyrene standards (from PolymerLaboratories) in conjunction with their elution volumes. The equivalentpolyethylene molecular weights are determined by using appropriateMark-Houwink coefficients for polyethylene and polystyrene (as describedby Williams and Ward in Journal of Polymer Science, Polymer Letters,Vol. 6, (621) 1968) to derive the following equation:

Mpolyethylene=a*(Mpolystyrene)^(b).

In this equation, a=0.4316 and b=1.0 (as described in Williams and Ward,J. Polym. Sc., Polym. Let., 6, 621 (1968)). Polyethylene equivalentmolecular weight calculations were performed using VISCOTEK TriSECsoftware Version 3.0.

Differential Scanning Calorimetry (DSC)

Differential Scanning calorimetry (DSC) is used to measure crystallinityin the polymers (e.g., ethylene-based (PE) polymers). About 5 to 8 mg ofpolymer sample is weighed and placed in a DSC pan. The lid is crimped onthe pan to ensure a closed atmosphere. The sample pan is placed in a DSCcell, and then heated, at a rate of approximately 10° C./min, to atemperature of 180° C. for PE (230° C. for PP). The sample is kept atthis temperature for three minutes. Then the sample is cooled at a rateof 10° C./min to −60° C. for PE (−40° C. for PP), and kept isothermallyat that temperature for three minutes. The sample is next heated at arate of 10° C./min, until complete melting (second heat). The percentcrystallinity is calculated by dividing the heat of fusion (H_(f)),determined from the second heat curve, by a theoretical heat of fusionof 292 J/g for PE (165 J/g, for PP), and multiplying this quantity by100 (for example, % cryst.=(H_(f)/292 J/g)×100 (for PE)).

Unless otherwise stated, melting point(s) (T_(m)) of each polymer isdetermined from the second heat curve (peak Tm), and the crystallizationtemperature (T_(c)) is determined from the first cooling curve (peakTc).

Elongation at break (cross direction (CD) and machine direction (MD)) ismeasured in accordance with BS ISO 37 Ed. 2012.

E-Modulus cross direction (CD) and machine direction (MD)) is measuredin accordance with BS ISO 37 Ed. 2012.

Tensile Strength (cross direction (CD) and machine direction (MD)) ismeasured in accordance with BS ISO 37 Ed. 2012.

Some embodiments of the present disclosure will now be described indetail in the following Examples.

EXAMPLES 1. Materials

Materials used in the inventive examples and the comparative samples areprovided in Tables 1-3 below. Polymers are typically stabilized with oneor more antioxidants and/or other stabilizers.

TABLE 1 Resin materials and properties MI (2.16 kg MFR (2.16 kg Density,Type at 190° C.) at 230° C.) g/cc Versify 3300 PBE 8 0.867 Inspire 137PP 0.75 0.900 OBC1 OBC 5 0.877 OBC2 OBC 0.5 0.877 Attane 4607G ULDPE 40.904 Hifax CA 10A PP 0.6 0.880 PP = propylene-based polymer ULDPE =ultra low density polyethylene

TABLE 2 Flame retardant materials and properties d50, Density, Typemicron g/cc Comment Magnifin H5 MDH 1.6-2 2.35 Uncoated, finelyprecipitated Magnifin H5 MDH 1.6-2 2.35 Propriety surface treatment, MVfinely precipitated

TABLE 3 Additive package (masterbatch)-composition Type *Wt % Versify2300 Carrier resin 35 Kronos 2220 TiO2 51 Irganox B225 Thermalstabilizer 4 Chimasorb 2020 HALS 10 *Wt % based on total wt masterbatch

2. Direct Addition

Examples 1-7 are examples of the high-load flame retardant TPOformulation. The Reference is a formulation with no flame retardant.Component proportions (in weight percent based on total weight of theformulation) are shown in Table 4.

TABLE 4 Formulations Versify HIFAX Inspire Attane Additive Wt % 3300 CA10A 137 OBC1 OBC2 4607 H5 H5 MV MB Example 1 47.7 11.9 35.8 4.6 Example2 35.8 23.8 35.8 4.6 Example 3 37.5 25.0 37.5 Example 4 31.7 21.2 47.1Example 5 37.5 25.0 37.5 Example 6 31.7 21.2 47.1 Example 7 24.0 16.060.0 Reference¹ 59.6 35.8 4.6 ¹Reference represents conventional TPOformulation. MB = additive masterbatch

3. Counter-Rotating Extrusion

The formulations (Examples 1-7) are directly added to an AMUTcounter-rotating twin screw extruder D=92 mm, L/D=36. The components ofthe formulations are fed directly into the extruder via two differentfeeders. The flame retardants are in powder form and fed into theextruder through a powder feeder. The polymer materials are in the formof granules and are fed into the extruder through a separate feeder. Themelting, mixing and extrusion is performed in a single step. Nocompounding step or pre-extrusion step is performed prior to thecomponents being directly added to the counter-rotating twin screwextruder. The formulations of Examples 1-7 are processed through acounter-rotating twin screw extruder under the processing conditionsshown in Table 5 below.

TABLE 5 Processing parameters for example 1-7 (Counter-rotating twinscrew: D = 92 mm, L/D = 36, die with = 700 mm) Die P, RPM ExtruderThroughput, bars screw Power, A kg/h Melt T, [max [max [max [max ° C.450 bar] 48] 180 A] 300 kg/h] Example 1 170 24 180 Example 2 171 159 2462 180 Example 3 175 254 24 93 180 Example 4 175 277 21 108 180 Example5 171 193 22 69 180 Example 6 173 220 22 74 180 Example 7 173 230 22 70180

The counter-rotating twin screw extrusion process produces TPO roofingmembranes with a thickness of 0.65 mm to 0.75 mm and a width of 700 mm.

TABLE 6 Mechanical performance (Counter-rotating twin screw: D = 92 mm,L/D = 36, die with = 700 mm) EN ISO EN ISO Tensile Tensile ElongationElongation 11925-2 11925-2 strength, strength, at break, at break,E-Modulus, E-Modulus, Class D Class D CD [MPa] MD [MPa] CD [%] CD [%] CD[MPa] MD [MPa] (surface) (edge) Requirement >10 >10 >500 >500 <100 <100Indicative Example 1 19.0 21.0 870 860 76.5 89.8 Pass Fail Example 214.3 14.3 1100 985 47.3 70.0 Pass Fail Example 3 25.8 22.6 800 750 83.781.4 Pass Fail Example 4 15.0 15.3 740 695 107.4 104.8 Pass Pass Example5 26.3 25.9 800 650 42.7 37.7 Pass Fail Example 6 18.4 18.8 760 735 50.548.7 Pass Fail Example 7 11.0 11.7 740 725 94.5 98.0 Pass Pass

Each of Examples 1-7 meets the mechanical properties for TPO roofingmembrane. In addition, each of Examples 1-7 meets classification D(class D) for the EN ISO 11925-2 surface exposure test.

Example 4 and Example 7 each meets classification D (class D) for the ENISO 11925-2 edge exposure test. EN ISO 11925-2 edge exposure test is anindicative test and is more stringent than EN ISO 11925-2 surfaceexposure test. The edge exposure test is applicable to the end use ofthe membrane.

For comparison, the formulations of Examples 1-7 and Reference are addedto a KrassMafei FEA-LAB-ZE25 co-rotating extruder. Subjected to theco-rotating extruder, the formulations of Examples 1-7 producerespective Comparative Samples 1-7. The Reference is a formulation withno flame retardant. No compounding or pre-extrusion step is performedprior to addition to the co-rotating twin screw extruder. Co-rotationtwin screw extrusion is performed under the conditions shown in Table 7.

TABLE 7* Processing parameters for example 1-7 (Co-rotating twin screw:D = 25 mm, L/D = 40, die with = 200 mm) Melt T, Die P, RPM Throughput, °C. bars screw kg/h Comparative 204 73 250 12 Sample 1 Comparative 204 78250 12 Sample 2 Comparative 207 120 250 12 Sample 3 Comparative 210 145280 12 Sample 4 Comparative 206 120 280 12 Sample 5 Comparative 208 110280 12 Sample 6 Comparative 208 120 280 12 Sample 7 Reference 208 105280 12 *Table 7 is comparative data

The properties for the TPO roofing membranes produced by way of theprocessing conditions of Table 7 are shown in Table 8 below.

TABLE 8* Mechanical performance (Co-rotating twin screw: D = 25 mm, L/D= 40, die with = 200 mm) EN ISO EN ISO Tensile Tensile ElongationElongation 11925-2 11925-2 strength, strength, at break, at break,E-Modulus, E-Modulus, Class D Class D CD [MPa] MD [MPa] CD [%] CD [%] CD[MPa] MD [MPa] (surface) (edge) Requirement >10 >10 >500 >500 <100 <100Indicative Comparative 19.1 23.9 985 580 98.7 83.8 Pass Fail Sample 1Comparative 12.5 16.7 1050 580 63.2 50.4 Pass Fail Sample 2 Comparative21.1 23.2 840 400 85.0 64.5 Pass Fail Sample 3 Comparative 16.7 16.8 790560 149.4 129.0 Pass Pass Sample 4 Comparative 23.6 18.0 790 470 67.044.9 Pass Fail Sample 5 Comparative 17.1 14.4 735 600 65.4 59.3 PassFail Sample 6 Comparative 11.5 12.0 710 685 72.7 110.4 Pass Pass Sample7 Reference 19.3 22.3 900 600 91 87 Pass Fail *Table 8 is comparativedata

5. Discussion

The present high-load flame retardant TPO formulations surprisinglyyield suitable TPO roofing membrane when directly added to a CRTSextrusion process. As shown in Table 6 above, the present processproduces TPO roofing membrane that meets the mechanical performancerequirements for TPO roofing membrane and also meets classification D ofEN ISO 11925-2, surface exposure test alone or in combination withmeeting classification D of EN ISO 11925.2, edge exposure test.

Bounded by no particular theory, it is believed the combination of theinventive high-load flame retardant TPO formulation in combination withCRTS extrusion works synergistically to promote dispersion, uniformity,and mechanical properties in order to produce a TPO roofing membrane.The olefin block copolymer and polyolefin polymer system enables uptakeof the high-load flame retardant. As such, the present process andhigh-load flame retardant TPO formulation unexpectedly promote uniformdispersion of the high-load flame retardant under the low shear an lowmass temperature conditions present during counter-rotating twin screwextrusion. The good mechanical performance and acceptable flameretardance of the present TPO roofing membranes is the result ofhomogeneous dispersion of high-load flame retardant particles throughoutthe OBC/polyolefin polymer matrix.

CRTS extrusion can be performed at a lower temperature (advantageouslyreducing production cost). CRTS extrusion also operates at a lower screwspeed, further reducing energy consumption during production. Inaddition, the low screw speed and lower extrusion temperature of thepresent CRTS extruder imparts less shear stress and less heat on theformulation resulting in less component degradation and preservation ofdesirable membrane properties.

It is specifically intended that the present disclosure not be limitedto the embodiments and illustrations contained herein, but includemodified forms of those embodiments including portions of theembodiments and combinations of elements of different embodiments ascome within the scope of the following claims.

1. A process comprising: directly adding components of a high-load flameretardant thermoplastic polyolefin (TPO) formulation to acounter-rotating twin screw extruder, the high-load flame retardant TPOformulation comprising an olefin block copolymer; a polyolefin; greaterthan 30 wt % of a granular flame retardant; extruding, withcounter-rotation of the twin screws, the components of the high-loadflame retardant TPO formulation; and forming a TPO roofing membranehaving a tensile strength (CD) greater than 10 MPa, and a flameretardance rating of classification D as measured in accordance with ENISO 11925-2, surface exposure test.
 2. The process of claim 1 comprisingforming a TPO roofing membrane having a flame retardance rating ofclassification D as measured in accordance with EN ISO 11925-2, edgeexposure test.
 3. The process of claim 1 comprising counter-rotating thetwin screws at a rotation rate from 15 rpm to 40 rpm.
 4. The process ofclaim 1 comprising performing the counter-rotating extrusion at atemperature less than 185° C.
 5. The process of claim 1 comprisingdirectly adding components of a high-load TPO formulation comprising 20wt % to 50 wt % olefin block copolymer; 10 wt % to 30 wt %ethylene/α-olefin copolymer; 35 wt % to 75 wt % of a flame retardant;and forming a TPO roofing membrane having a tensile strength (CD)greater than 10 MPa; an elongation at break greater than 500%; and anE-modulus less than 100 MPa.
 6. The process of claim 1 comprisingdirectly adding components of a high-load flame retardant TPOformulation comprising 20 wt % to 40 wt % olefin block copolymer; 15 wt% to 30 wt % ethylene/α-olefin copolymer having a density from 0.90 g/ccto 0.91 g/cc; 35 wt % to 60 wt % of a flame retardant; 1 wt % to 5 wt %additive; and forming a TPO roofing membrane having a tensile strengthfrom greater than 10 MPa to 25 MPa; an elongation at break from greaterthan 500% to 1100%; and an E-modulus less than 100 MPa.
 7. A processcomprising: directly adding components of a high-load flame retardantthermoplastic polyolefin (TPO) formulation to a counter-rotating twinscrew extruder, the high-load flame retardant TPO formulation comprisinga propylene-based elastomer; a polyolefin; greater than 30 wt % of agranular flame retardant; extruding, with counter-rotation of the twinscrews, the components of the high-load flame retardant TPO formulation;and forming a TPO roofing membrane having a tensile strength (CD)greater than 10 MPa, and a flame retardance rating of classification Das measured in accordance with EN ISO 11925-2, surface exposure test.